For a positively charged particle moving in a `x-y` plane initially along the `x-axis` , there is a sudden change in its path due to the presence of electric and//or magnetic fields beyond `p` . The curved path is shown in the ` x- y `plane and is found to be non - circular. Which one of the following combinations is possible ?

Options

A. `vecE=0, vecB=bhati+chatk`
B. `vecE=ahati, vecB=chatk+ahati`
C. `vecE=0, vecB=chatj+bhatk`
D. `vecE=ahati, vecB=chatk+bhatj`

Answer

b

Explanation

The velocity at P is in the x direction (given). Let `vecV=mhati`.
After P, the positively charged particle gets deflected in the
x-y plane toward-y direction and the path is non-circular.
Now, `vecF=q(vecvxxvecB)`
`=q[mhatixx(chatk+ahati)]` [for option (b)]
`=q[mchatixxhatk+mahatixxhati]=mcq(-hatj)`
Since in option (b) electric field is present, i.e., `vecE=ahati`,
therefore, it will also exert a force in the +x direction. The
net result of the two forces will be a non-circular path.
Only option (b) fits for the above logic. For other options,
we get some other results.